What I did was to buy some 1/4" vinyl tubing at homedepot. I cut it slightly longer than the circumference of the opening. Test fit the tubing to make sure that when you lay it on the edge of the cutout opening to it makes for a tight fit. Put your adhesive on the passive, lay it in the opening, then place the vinyl tubing in to hold it in place. The tightness of the vinyl tubing wedged in the opening will be enough to hold the passive in while the glue dries and you can do all of them at the same time.

I did one at a time using a rolled up strip of cardboard to press down on the seal. You roll up a strip of cardboard and when it fits inside the cutout you fasten it with tape. Then you can place a platter on top and add weights. This makes a nice airtight seal. I´d say the weldbond will be dry after about 20 min.

This is overkill. Just apply the glue to both sides, wait 10 minutes or so to let the glue setup a little. Then just put it in place and run your finder over and around it to press it into place. No need for weights and stuff like that. Zygi confirmed this in this thread...

I second Gnat leader. You do not need to weigh down the passives because the Weldbond sets up so quickly.

Apply the glue on the passive and the wood. Put it in place. The router groove will hold it in place. Then take a blunt object and go around the entire passive every 10 minutes, squeezing out any airpockets.

EDIT---You can apply the weight if you want I guess, nothing wrong with having the comfort of knowing the passive is flush and perfect.